1. Field of the Invention
The present invention relates to a cushion, such as for use as a mattress or seat and backrest, for example, which presents an outer surface of selectively variable temperature and apparatus therefor including a heat pump for reducing cushion temperature operating on a Stirling cycle.
2. Description of Related Art
There are many situations in which it is desirable that a cushion, such as a seat and backrest in an automotive vehicle, for example, be selectively cooled or heated for the comfort of someone sitting or resting against the cushion. In the colder climates, it would be desirable, particularly in the winter time, to obtain relatively instant heating of the seat cushions to warm an individual sitting or leaning on them prior to normal actuation of the auto heating system which typically relies upon the engine coolant being brought up to a sufficiently high temperature for satisfactory operation. In warm seasons, these same vehicles which have conventional air conditioning systems that direct cool air directly on the front of passengers and into the vehicle interior generally, undesirably leave those portions of the individual directly facing and contacting the seat and backrest cushions at an undesirably elevated temperature and, in the case of high humidity, this results in even more discomfort for the vehicle occupant. In both situations, warming or cooling, as the case may be, of the cushions themselves will increase the comfort level of the individual.
Because of believed deleterious effect upon the environment, certain of the more efficient chemical materials (e.g., Freon) are being forced into retirement from use in air conditioning systems. At the present time, all other substitute materials known for this purpose do not possess the same high level of efficiency and are, in truth, substantially inferior in normal operation to those being eliminated. Also, there is the increasing problem that future automotive vehicles may be required to operate on less and less power in order to conserve basic fuels as well as reduce harmful byproducts, and this will, of necessity, leave a lesser proportion of available power for use by air conditioning or heating equipment.
In U.S. Pat. No. 5,002,336, by Steve Feher, there is disclosed a seat and backrest especially constructed for being cooled or heated as desired where the heat pump utilized for this purpose is a thermoelectric unit which accomplishes the desired function with a substantially lower energy requirement than is utilized where the full interior of the vehicle is conditioned in accordance with conventional air conditioning techniques. However, even though considered a substantial improvement over other known and conventional techniques, there is still believed to be room for improvement especially in increasing overall efficiency of operation.
In the '336 patent, the seat and backrest construction includes a plenum for receiving temperature conditioned air, which construction is formed alternatively from either metal wire spring coils or relatively rigid solid plastic tubes with sidewall openings formed therein. To function properly the seat construction must readily allow temperature conditioned air to pass throughout the entire plenum, not close off conditioned air flow to a significant extent from the weight of an individual sitting or leaning on the seating, and at the same time be comfortable.
Still further, automotive seat manufacturer's consider it undesirable that internal supports (e.g., spring coils) should produce a visible surface impression and in that way destroy design esthetics. For example, wire plenum coils and rigid plastic tubes end to "mark" the outermost seat covering (e.g., leather) which is undesirable. Also, it has been found in this regard to be self defeating to merely increase the thickness of a comfort layer located over wire springs or rigid plastic tubes since this reduces heat transference to the extent that overall operational efficiency is reduced.
A persistent problem with wire coils used to form a plenum in a seat such as a vehicle seat is that the coils spread the load weight too evenly giving the sensation of sitting "on top" of the seat rather than in the seat. Accordingly, an individual using the seat may often experience a lack of orthopedic support.